A cleaning method compatible with multiple types of battery rework pieces

Abstract

This disclosure relates to the field of photovoltaic solar cell manufacturing technology, specifically to a cleaning method compatible with multiple types of rework wafers. The cleaning method includes classifying the rework wafers according to their degree of contamination, and then performing different cleaning treatments based on the classification: Type A rework wafers: surface only contaminated; the cleaning process includes water washing and slow lifting. Type B rework wafers: containing at least one of a poly film, a boron layer, and a passivation film; the cleaning process includes graded texturing. Type C rework wafers: containing laser residue; the cleaning process includes alkaline polishing and graded texturing. This cleaning method can adapt to all types of rework wafers, including conventional TOPCon, TOPCon-BC, laser polyfing, and photolithographic patterned wafers, addressing core issues such as laser markings, photolithographic residues, and deep silicon damage. After cleaning, the silicon wafers are free of visible marks, color differences, and residual impurities, while controlling the amount of silicon wafer thinning and efficiency loss.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic solar cell manufacturing technology, and more specifically, to a cleaning method compatible with reworked cells of multiple types of cells. Background Technology

[0002] Currently, high-efficiency N-type TOPCon cells have become the mainstream mass-produced product in the photovoltaic industry, with a continuously increasing market share. Simultaneously, advanced process upgrades such as TOPCon-BC composite structures, laser polyfing finger-shaped patterning, and precision photolithography patterning have led to continuous breakthroughs in cell conversion efficiency, making it a core direction for the high-quality development of the photovoltaic industry. However, in actual production processes, various factors such as equipment parameter fluctuations, process debugging deviations, production environment interference, and operator errors result in a large number of defective reworked cells at each stage. The efficient recycling and reuse of these reworked cells is a crucial link in reducing production costs, improving capacity utilization, and enhancing the market competitiveness of enterprises.

[0003] Existing TOPCon rework cell cleaning processes are mostly designed only for single conventional TOPCon cells. These processes are limited in scope and cannot accommodate rework cells with multi-process composite structures. They also suffer from several core technical defects, severely restricting the efficiency and quality of rework cell recycling and reuse. Firstly, the classification of reworked parts is cumbersome and complicated. Different types of reworked parts require multiple dedicated equipment and multiple independent production lines for separate processing, which not only significantly increases equipment investment costs but also occupies a large amount of workshop production space, while increasing the difficulty and cost of operation and maintenance management. Secondly, for defective rework wafers with laser isolation grooves and Polyfing laser patterned markings on the back of TOPCon-BC batteries, the existing conventional acid and alkali cleaning process for processing defective rework wafers can only remove the surface passivation film and polycrystalline silicon film layer. It cannot effectively remove the laser-induced silicon substrate lattice damage, surface heavy doping variation layer, and local thermal oxidation layer. After cleaning, obvious laser damage marks are still left on the silicon wafer surface, resulting in severe color difference, uneven electrical performance distribution, and extremely low rework yield of the rework wafers. Third, for rework wafers produced by photolithography patterning process, the photoresist, development residue, and etching byproducts on their surface have strong adhesion, and conventional cleaning processes for rework wafers cannot completely remove them, which can easily cause contamination on the silicon wafer surface and blockage of micropores, affecting the normal operation of subsequent processes. Fourth, cross-contamination can easily occur when various types of reworked wafers are mixed in the same production line. Excessive etching can lead to excessive thinning of silicon wafers and a high breakage rate, which in turn causes a significant decrease in battery conversion efficiency and affects the reuse value of reworked wafers. Fifth, the process adaptability is extremely poor, making it impossible to achieve graded and flexible processing of different types of rework pieces using a single piece of equipment and a unified tank. Mass production continuity is poor, making it difficult to adapt to the needs of large-scale mass production. Sixth, the differences in cleaning time for various rework pieces, the cumulative number of cleanings, and the impact of prolonged periods without cleaning on the lifespan of the cleaning solution were not fully considered. This resulted in the cleaning solution being prone to failure and being consumed quickly. Frequent replacement of the cleaning solution further increased production costs, and the failure of the cleaning solution could lead to unstable cleaning results, which seriously affected the yield of rework pieces. Currently, there is no unified, graded cleaning process in the photovoltaic industry that is compatible with the four types of rework wafers: conventional TOPCon, TOPCon-BC, laser Polyfing, and photolithographic patterning. Most existing processes can only handle a single type of rework wafer and lack specific solutions for issues such as laser markings, photolithography residues, and localized deep damage, resulting in poor rework and reuse performance. Furthermore, existing processes generally lack effective means of controlling the lifespan of cleaning solutions, failing to address issues such as cleaning time variations, cumulative cleaning cycles, and solution failure due to inactivity. This makes it difficult to meet the needs of enterprises for large-scale, low-cost, and high-yield rework wafer recycling.

[0004] In view of this, this disclosure is hereby made. Summary of the Invention

[0005] The purpose of this disclosure is to provide a cleaning method compatible with various types of rework wafers. The cleaning method provided in the embodiments of this disclosure can adapt to all types of rework wafers, including conventional TOPCon, TOPCon-BC, laser Polyfing, and photolithographic patterning wafers. In particular, it addresses core issues such as laser markings, photolithography residues, and deep silicon damage. After cleaning, the silicon wafers are free of visible markings, color differences, and residual impurities, increasing the rework yield to ≥97%, significantly improving the reuse value of rework wafers, and controlling the amount of silicon wafer thinning and efficiency loss.

[0006] This disclosure is implemented as follows: In a first aspect, this disclosure provides a cleaning method compatible with multiple types of reworked battery cells, comprising: classifying the reworked cells according to their degree of contamination, and then performing different cleaning treatments according to the classification; wherein the classification and cleaning treatments are as follows: (1) Class A reworked sheets: The surface is only contaminated, without Poly film, boron layer and passivation film; The cleaning process for the Class A rework pieces includes: water washing and slow lifting; (2) Class B rework sheets: containing at least one of Poly film, boron layer and passivation film; The cleaning process for the Class B rework pieces includes: first water wash, first acid wash, second water wash, graded flocking, third water wash, alkaline wash, fourth water wash, second acid wash, fifth water wash, and slow lifting; (3) Category C rework pieces: containing laser residue; The cleaning process for the Class C rework pieces includes: first water wash, first acid wash, second water wash, alkaline polishing, third water wash, graded flocking, fourth water wash, alkaline wash, fifth water wash, second acid wash, sixth water wash, and slow lifting.

[0007] In an optional embodiment, the first pickling process in the cleaning process of the Class B rework piece includes cleaning with HF and HCl. Preferably, the conditions for the first pickling during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of HF is 3-8%; the initial concentration of HCl is 1-5%; the initial concentration of rework additive is 1-5%; (2) the self-replenishing concentration of HF is 0.03-0.08%; the self-replenishing concentration of HCl is 0.01-0.05%; the self-replenishing concentration of rework additive is 0.01-0.05%.

[0008] In an optional embodiment, the grading and texturing process during the cleaning of the Class B rework sheets includes treatment with hydroxides and alcohol solvents; preferably, the hydroxides include sodium hydroxide and the alcohol solvents include isopropanol. Preferably, the grading and texturing conditions during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.8-1.2%, and the initial concentration of the alcohol solvent is 2-3%; (2) the self-replenished concentration of the hydroxide is 0.02-0.06%, and the self-replenished concentration of the alcohol solvent is 0.01-0.04%; (3) the temperature is 75-80℃, and the time is 30-40s.

[0009] In an optional embodiment, the alkaline washing process in the cleaning process of the Class B rework sheet includes: cleaning with hydroxide and oxidant, preferably, the hydroxide includes sodium hydroxide and the oxidant includes hydrogen peroxide; Preferably, the alkaline washing conditions during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.7-2% and the initial concentration of the oxidant is 1.3-2.5%; (2) the self-replenished concentration of the hydroxide is 0.015-0.04% and the self-replenished concentration of the oxidant is 0.02-0.08%.

[0010] In an optional embodiment, the second pickling process in the cleaning process of the Class B rework piece includes cleaning with HF; Preferably, the conditions for the second acid washing during the cleaning process of the B-type rework piece meet at least one of the following requirements: (1) the initial concentration of the HF is 0.8-4%; (2) the self-replenishing concentration of the HF is 0.05-0.3%; and (3) the cleaning time is 150-400s.

[0011] In an optional implementation, if the C-type rework sheet contains photoresist, the cleaning process of the C-type rework sheet further includes: removing the photoresist before the first water wash; Preferably, the degumming process includes: using an oxidizing agent and a strong acid for degumming; Preferably, the oxidant includes hydrogen peroxide, and the strong acid includes sulfuric acid; Preferably, the conditions for degumming meet at least one of the following requirements: (1) the initial concentration of the strong acid is 65-85% and the initial concentration of the oxidant is 15-25%; (2) the concentration of the self-replenishing strong acid is 0.05-0.15% and the concentration of the self-replenishing oxidant is 0.05-0.15%; (3) the temperature is 90-120℃ and the time is 1800-2000s.

[0012] In an optional embodiment, the first acid wash in the cleaning process of the C-type rework sheet includes cleaning with HF and HCl; Preferably, the conditions for the first pickling during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of HF is 3-8%; the initial concentration of HCl is 1-5%; the initial concentration of rework additive is 1-5%; (2) the self-replenishing concentration of HF is 0.03-0.08%; the self-replenishing concentration of HCl is 0.01-0.05%; the self-replenishing concentration of rework additive is 0.01-0.05%.

[0013] In an optional embodiment, the alkaline polishing process during the cleaning of the Class C rework sheet includes: using hydroxide and ADDI; Preferably, the hydroxide comprises sodium hydroxide; The alkaline polishing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 5-7%; the initial concentration of the ADDI is 0.4-0.5%; (2) the self-replenished concentration of the hydroxide is 0.08-0.1% and the self-replenished concentration of the ADDI is 0.04-0.05%; (3) the temperature is 70-75℃ and the time is 450-600s.

[0014] In an optional embodiment, the grading and texturing of the Class C rework sheets includes treatment with hydroxides and alcohol solvents; preferably, the hydroxides include sodium hydroxide and the alcohol solvents include isopropanol. Preferably, the grading and texturing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.8-1.2%, and the initial concentration of the alcohol solvent is 2-3%; (2) the self-replenished concentration of the hydroxide is 0.02-0.06%, and the self-replenished concentration of the alcohol solvent is 0.01-0.04%; (3) the temperature is 75-80℃, and the time is 30-40s.

[0015] In an optional embodiment, the alkaline washing of the Class C rework sheets is carried out using hydroxides and oxidants. Preferably, the hydroxides include sodium hydroxide and the oxidants include hydrogen peroxide. Preferably, the alkaline washing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.7-2%, and the initial concentration of the oxidant is 1.3-2.5%; (2) the self-replenished concentration of the hydroxide is 0.015-0.04%, and the self-replenished concentration of the oxidant is 0.02-0.08%. Preferably, the second pickling process in the cleaning process of the C-type rework piece includes cleaning with HF; Preferably, the conditions for the second acid washing during the cleaning process of the C-type rework piece meet at least one of the following requirements: (1) the initial concentration of the HF is 0.8-4%; (2) the self-replenishing concentration of the HF is 0.05-0.3%; and (3) the cleaning time is 150-400s.

[0016] The present disclosure has the following beneficial effects: (1) The cleaning method provided in the embodiments of the present disclosure realizes the unified classification of rework pieces of all categories. The classification standard is clear, without omissions or overlaps. The production line is easy to sort and the equipment is easy to adapt. No new special equipment is required, which greatly reduces equipment investment and workshop space occupation, and reduces operation and maintenance management costs.

[0017] (2) The cleaning method provided in this embodiment adopts a cleaning system that integrates three independent processes, which can achieve one-click automatic switching, adaptive adjustment of parameters such as drug concentration, temperature, and time, automatic bypass of processes, simple and convenient operation, and is suitable for fully automated mass production lines, effectively improving production efficiency and reducing the intensity of manual operation.

[0018] (3) The cleaning method provided in this embodiment can specifically solve core problems such as laser imprints, photolithography residues, and deep silicon damage. After cleaning, the silicon wafer has no visible imprints, no color difference, and no residual impurities. The rework yield is increased to ≥97%, which greatly enhances the reuse value of rework wafers.

[0019] (4) The cleaning method provided in this embodiment strictly controls the silicon wafer thinning amount (B type ≤ 5 μm, C type ≤ 8 μm) and efficiency loss (≤ 0.2%), ensuring that the electrical performance of the reworked wafer is close to that of the original wafer, further enhancing the reuse value and market competitiveness of the reworked wafer.

[0020] (5) The cleaning method provided in this embodiment effectively extends the service life of the liquid by 30%-50%, reduces the frequency of liquid replacement by more than 40%, reduces the cost of rework liquid per piece by 35%, and at the same time reduces waste liquid discharge, reduces environmental protection pressure, and achieves green production.

[0021] (6) The cleaning method provided in this embodiment is closed-loop and controllable. The graded cleaning design avoids cross-contamination of various rework pieces, eliminates the need for frequent manual mixing of chemicals, reduces the workload of manual operation and maintenance, improves the stability and consistency of the production process, and ensures the quality of products produced in batches. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic flowchart illustrating a cleaning method compatible with reworked cells of multiple battery types provided in this embodiment of the disclosure; Figure 2 A flowchart illustrating the cleaning method for reworked battery cells provided as a comparative example of this disclosure; Figure 3 This is a diagram of the reworked sheet after cleaning, provided in Embodiment 3 of this disclosure; Figure 4 A diagram of the reworked piece after cleaning, provided as Comparative Example 1 of this disclosure; Figure 5 A diagram of the reworked piece before cleaning, provided in Comparative Example 2 of this disclosure; Figure 6 This is a diagram of the reworked piece after cleaning, provided as Comparative Example 2 of this disclosure. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] As described in the background section, existing cleaning methods for reworked wafers have the following problems: 1. Existing technologies cannot fully cover all types of rework wafers, including conventional TOPCon, TOPCon-BC, laser Polyfing, and photolithography patterning. They can only process a single type, have extremely poor adaptability, require multiple machines to process on separate lines, significantly increase equipment investment and maintenance costs, and occupy a large amount of workshop space.

[0026] 2. For TOPCon-BC laser isolation grooves and Polyfing laser imprints, existing conventional cleaning processes cannot effectively remove laser-induced silicon substrate damage. The residues after cleaning are obvious, resulting in severe color difference, uneven distribution of electrical properties, and low rework yield of rework wafers, which affects their reuse value.

[0027] 3. The photoresist residue and etching byproducts on the rework wafers with photolithography patterns have strong adhesion and cannot be completely removed by conventional processes. This can easily cause contamination on the silicon wafer surface and blockage of micropores, affecting the normal progress of subsequent processes such as coating and printing, and reducing the yield of rework wafers.

[0028] 4. Mixing various types of reworked wafers in the same production line can easily lead to cross-contamination. Excessive corrosion can cause silicon wafers to be thinned beyond the standard, resulting in a high breakage rate and a significant decrease in cell efficiency, further reducing the reuse value and economic benefits of reworked wafers.

[0029] 5. The lack of graded cleaning design and the rigid, single-process design make it impossible to flexibly process different types of rework pieces on a single machine, resulting in poor production continuity and difficulty in adapting to large-scale production needs.

[0030] 6. The differences in cleaning time for different types of rework tablets, the cumulative number of cleaning cycles, and the impact of prolonged periods without cleaning on the lifespan of the cleaning solution were not considered. The cleaning solution is prone to failure and is consumed quickly. Frequent solution changes increase production costs, and the cleaning effect is unstable, which seriously affects the yield of rework tablets.

[0031] The cleaning method for reworked cells compatible with multiple types of batteries disclosed in this disclosure can effectively improve or solve the above-mentioned problems. Specifically, this cleaning method (see...) Figure 1 This includes classifying the reworked pieces according to their degree of contamination, and then performing different cleaning treatments based on the classification. Specifically, the classification and cleaning treatments are as follows: I. Rework wafers with only water-washable contaminants on their surface, and lacking poly film, boron layer, and passivation film, are classified as Class A rework wafers. These rework wafers do not undergo acid washing or texturing, and are not subjected to additional thinning to avoid unnecessary thickness loss of the silicon wafer. Class A rework wafers only undergo water washing and slow pulling. Class A rework wafers mainly originate from boron expansion pre-expansion processes.

[0032] Among them, the water washing of Class A rework wafers: deionized water is used to rinse off the desorbed impurities and residual chemicals on the silicon wafer surface, with a set time of 100-150 seconds, and the overflow mode adopts basket overflow.

[0033] Slow lifting of Class A rework pieces: Set the process temperature to 20-30℃, use a robotic arm to lift, and use a straight basket overflow mode.

[0034] Type A rework wafers are classified as slightly contaminated. Currently, the conventional methods are to directly retexturize the wafers or clean them using a conventional rework machine. The drawbacks of this approach are: ① dust contamination will remain on the surface of the silicon wafers after texturing; ② direct cleaning with a rework machine will lead to excessive thinning of the silicon wafers. The method provided in this disclosure, however, will not cause thinning.

[0035] II. Rework sheets containing at least one of Poly film, boron layer, and passivation film are classified as Category B rework sheets. These rework sheets mainly originate from rework sheets after boron expansion but before screen printing. The cleaning process for Category B rework sheets includes: first water wash, first acid wash, second water wash, grading and texturing, third water wash, alkaline wash, fourth water wash, second acid wash, fifth water wash, and slow lifting. The specific process is as follows: First water rinse: Use deionized water to rinse away desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use basket overflow mode. (This is for organic dirt or particulate matter present during the rework wafer collection process).

[0036] First pickling: Cleaning is performed using HF and HCl. The washing time is 1500-2000 seconds. The initial HF concentration is selected as 3-8%, for example, any value between 3%, 4%, 5%, 6%, 7%, 8%, or 3-8%, preferably 6%. The initial HCl concentration is selected as 1-5%, for example, any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, preferably 3%. The initial rework additive concentration is selected as 1-5%, for example, any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, preferably 3%. The self-replenishing HF concentration is selected as 0.03-0.08%, for example, any value between 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.03-0.08%, preferably 0.05%. The concentration of self-replenishing HCl is selected from 0.01-0.05%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.01-0.05%, preferably 0.02%. The concentration of self-replenishing rework additive is selected from 0.01-0.05%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.01-0.05%, preferably 0.03%. A continuous circulation, basketless bubbling mode is used. The poly membrane and boron-rich layer (BSG) are rapidly peeled off using a mixture of HF + HCl + rework additive.

[0037] This disclosure reveals that when the initial concentrations of HF, HCl, and rework additive are below 3%, 1%, 0.03%, 0.01%, and 0.01%, respectively, the reaction rate is too slow, preventing the poly film from completely separating from the boron-rich layer and resulting in residual contamination. Conversely, when the initial concentrations of HF and HCl are above 8%, 5%, and 0.08%, 0.05%, respectively, the reaction rate is too fast, leading to excessive etching of the silicon wafer and resulting in abnormal appearance.

[0038] Second water wash: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0039] Grading and texturing: This involves treatment with hydroxides and alcohol solvents; wherein the hydroxide includes sodium hydroxide, and the alcohol solvent includes isopropanol. Specifically, the process temperature is set to 75-80℃, for example, any value between 75℃ and 80℃, such as 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, etc. The washing time is 30-40 seconds, for example, any value between 30s, 31s, 32s, 33s, 34s, 35s, 36s, 37s, 38s, 39s, 40s, or 30-40s, preferably 35s. The initial NaOH concentration is selected as 0.8-1.2%, for example, any value between 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, or 0.8-1.2%, preferably 1.0%. The initial IPA concentration is 2-3%, for example, any value between 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or 2-3%, preferably 2.5%. The initial flocking conditioner concentration is selected as 0.15%, and the self-replenishing NaOH concentration is selected as 0.02-0.06%, for example, any value between 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, or 0.02%-0.06%, preferably 0.04%. The self-replenishing IPA concentration is selected as 0.01-0.04%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, or 0.01-0.04%, preferably 0.03%. A continuous circulation, basketless bubbling mode is used.

[0040] This study utilizes a gentle texturing process to optimize the surface texture of silicon wafers, resolving issues of whitening and color difference after cleaning. Conventional processes lack this graded texturing step, resulting in a color difference ΔE > 3.0 and a high defect rate after cleaning. The research revealed that when the process temperature is below 75℃, the time is below 30s, the NaOH concentration is below 0.8%, and the IPA concentration is below 2%, the texturing effect is insufficient, failing to eliminate color difference. Conversely, when the process temperature is above 80℃, the time is above 40s, the NaOH concentration is above 1.2%, and the IPA concentration is above 3%, excessive thinning occurs, with a total wafer thinning exceeding 5μm. Only when the process temperature is 75-80℃, the time is 30-40s, the initial NaOH concentration is 0.8-1.2%, the IPA concentration is 2-3%, and self-compensating concentration matching is achieved, resulting in the optimal texturing effect: color difference ΔE < 1.5, thinning ≤ 1μm, and total thinning ≤ 5μm.

[0041] Third water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0042] Alkaline washing: Cleaning is performed using hydroxides and oxidants, wherein the hydroxide includes sodium hydroxide and the oxidant includes hydrogen peroxide. Specifically, the cleaning time is 150-200 seconds, the temperature is 63-68°C, and the initial hydroxide concentration is selected as 0.7-2%, for example, any value between 0.7%, 1%, 1.5%, 2%, or 0.7-2%; preferably 1%. The initial hydrogen peroxide concentration is 1.3-2.5%, preferably any value between 1.3%, 1.5%, 1.8%, 2%, 2.5%, or 1.3-2.5%, preferably 1.8%. The self-replenishing hydroxide concentration is selected as 0.015-0.04%, for example, any value between 0.015%, 0.02%, 0.03%, 0.03.5%, 0.04%, or 0.015-0.04%. Preferably 0.025%. The concentration of the self-replenishing hydrogen peroxide is selected from 0.02-0.08%, for example, any value between 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.02-0.08%; preferably 0.05%, using a continuous circulation, basket bubbling mode. Alkaline washing removes residual reaction products and simultaneously cleans organic contaminants from the surface.

[0043] This disclosure reveals that when the process temperature is below 60°C, the NaOH concentration is below 0.7%, the H2O2 concentration is below 1.3%, the self-replenished NaOH concentration is below 0.015%, and the self-replenished H2O2 concentration is below 0.02%, the alkaline washing effect decreases, reaction products remain, and subsequent electrical performance becomes abnormal. Conversely, when the process temperature is above 68°C, the NaOH concentration is above 2%, the H2O2 concentration is above 2.5%, the self-replenished NaOH concentration is above 0.04%, and the self-replenished H2O2 concentration is above 0.08%, hydrogen peroxide decomposes too quickly, leading to excessive alkaline etching and excessive silicon wafer thinning.

[0044] Fourth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0045] Second pickling: This includes cleaning with HF. Specifically, the cleaning time is 150-400 seconds, preferably 300 seconds. The initial HF concentration is 0.8-4%, for example, any value between 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 0.8-4%; preferably 2%. The self-replenishing HF concentration is 0.05-0.3%, for example, any value between 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or 0.05-0.3%, preferably 0.1%. A continuous circulation, basketless bubbling mode is used. HF neutralizes residual alkali and simultaneously removes the surface oxide layer.

[0046] This disclosure reveals that when the time is less than 150 seconds, the HF concentration is below 0.8%, and the self-replenishing HF concentration is below 0.05%, resulting in incomplete neutralization of alkali residue and incomplete removal of the surface oxide layer (poor dehydration). Conversely, when the time exceeds 400 seconds, the HF concentration is above 4%, and the self-replenishing HF concentration is below 0.3%, leading to disrupted overall robotic arm operation and chemical waste. Only when the time is 300 seconds, the HF concentration is 2%, and the self-replenishing HF concentration is 0.1%, is the oxide layer completely removed, resulting in optimal dehydration.

[0047] Fifth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0048] Slow lifting: Set the process temperature to 20-30℃, use a robotic arm to lift, and use a straight basket overflow mode.

[0049] 3. Rework pieces containing laser residue, such as BC laser isolation groove imprint rework pieces, Polyfing laser imprint rework pieces, and photolithography residue rework pieces, are classified as Class C rework pieces. The cleaning process for Class C rework pieces includes: first water wash, first acid wash, second water wash, alkaline polishing, third water wash, graded texturing, fourth water wash, alkaline wash, fifth water wash, second acid wash, sixth water wash, and slow lifting.

[0050] When a rework wafer contains photoresist, it is considered a photoresist residue rework wafer. The photoresist removal process is performed first. The photoresist removal process includes: using an oxidant and a strong acid to remove the photoresist; the oxidant includes hydrogen peroxide, and the strong acid includes sulfuric acid.

[0051] The process temperature was set at 90-120℃, the cleaning time at 1800-2000 seconds, the initial H2SO4 concentration at 65-85%, the initial H2O2 concentration at 15-25%, the self-replenishing H2SO4 concentration at 0.05-0.15%, and the self-replenishing H2O2 concentration at 0.05-0.15%. A continuous circulation, basket-bubbling mode was used. Utilizing the strong oxidizing properties of sulfuric acid and hydrogen peroxide, the photoresist residue and etching byproducts were thoroughly removed. Conventional processes lack this photoresist removal step, making it impossible to remove photoresist residue.

[0052] In this disclosure, when the temperature is below 90℃ and the time is below 1800s, the photoresist cannot be completely removed, leaving obvious residue. When the temperature is above 130℃ and the time is above 2000s, the energy consumption is too high, increasing the cost. Only when the temperature is between 90-120℃ and the time is between 1800-2000s can the photoresist residue be completely removed, with a residue of ≤1ppm.

[0053] First wash: Use deionized water to rinse away desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds, and use a basket overflow mode. Collect any organic dirt or particulate matter present during the rework wafer collection process.

[0054] First pickling: Cleaning is performed using HF and HCl. The washing time is 1500-2000 seconds. The initial HF concentration is selected as 3-8%, for example, any value between 3%, 4%, 5%, 6%, 7%, 8%, or 3-8%, preferably 6%. The initial HCl concentration is selected as 1-5%, for example, any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, preferably 3%. The initial rework additive concentration is selected as 1-5%, for example, any value between 1%, 2%, 3%, 4%, 5%, or 1-5%, preferably 3%. The self-replenishing HF concentration is selected as 0.03-0.08%, for example, any value between 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.03-0.08%, preferably 0.05%. The concentration of self-replenishing HCl is selected from 0.01-0.05%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.01-0.05%, preferably 0.02%. The concentration of self-replenishing rework additive is selected from 0.01-0.05%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.01-0.05%, preferably 0.03%. A continuous circulation, basketless bubbling mode is used. The poly membrane and boron-rich layer (BSG) are rapidly peeled off using a mixture of HF + HCl + rework additive.

[0055] In this embodiment, when the initial HF concentration is below 3%, the initial HCl concentration is below 1%, the initial rework additive concentration is below 1%, the self-replenishing HF concentration is below 0.03%, the self-replenishing HCl concentration is below 0.01%, and the self-replenishing rework additive concentration is below 0.01%, the reaction rate will be too slow, and the Poly film and boron-rich layer cannot be completely separated, resulting in residual contamination. When the initial HF concentration is above 8%, the initial HCl concentration is above 5%, the initial rework additive concentration is below 5%, the self-replenishing HF concentration is above 0.08%, the self-replenishing HCl concentration is above 0.05%, and the self-replenishing rework additive concentration is below 0.05%, the reaction rate will be too fast, the silicon wafer will be over-etched, and abnormal appearance will result.

[0056] Second water wash: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0057] Alkaline polishing: Alkaline polishing is performed using hydroxides and ADDI, where the hydroxides include sodium hydroxide. Specifically, the process temperature is set to 70-75℃, the time is set to 450-600s, the initial NaOH concentration is selected as 5-7%, the initial ADDI concentration is selected as 0.4-0.5%, the self-replenishing NaOH concentration is selected as 0.08-0.1%, and the self-replenishing ADDI concentration is selected as 0.04-0.05%. A continuous circulation, basketless bubbling mode is used to remove residual poly layer and level the surface.

[0058] For example, in the BC laser isolation groove rework process, alkaline polishing is performed with the following steps: the process temperature is set at 72℃, the time is set at 600s, the initial NaOH concentration is selected as 6%, the initial ADDI concentration is selected as 0.45%, the self-replenishing NaOH concentration is selected as 0.1%, and the self-replenishing ADDI concentration is selected as 0.045%. A continuous circulation, basketless bubbling mode is used. By extending the alkaline polishing time and increasing the alkaline concentration, the silicon substrate damage layer caused by the laser isolation groove is etched smooth, completely removing the laser imprint. Conventional alkaline polishing processes only last 480 seconds, which cannot remove the damage layer, leaving obvious imprint residue.

[0059] In this disclosure, when the alkaline polishing time is less than 600s and the NaOH concentration is less than 6%, the damaged layer cannot be completely etched away, leaving residual marks. When the time is greater than 650s and the NaOH concentration is greater than 7%, the thinning exceeds the standard. Only when the time is 600s-650s and the NaOH concentration is 6-7%, the damaged layer is completely removed, the marks are not visible to the naked eye, and the color difference ΔE < 1.5.

[0060] For example, consider the rework of Polyfing laser-imprinted wafers: Alkali polishing: The process temperature is set at 70℃, the time is set at 480s, the initial NaOH concentration is selected as 5%, the initial ADDI concentration is selected as 0.5%, the self-replenishing NaOH concentration is selected as 0.09%, and the self-replenishing ADDI concentration is selected as 0.05%, using a continuous circulation, basketless bubbling mode. By optimizing the additive concentration, the leveling effect of alkaline polishing is enhanced, the lattice damage layer caused by Polyfing laser is etched flat, and the laser grid imprint is completely removed. Conventional processes do not have this optimization, and the imprint residue is obvious.

[0061] In this disclosure, when the ADDI concentration is below 0.4%, the leveling effect is insufficient, and residual marks remain. When the ADDI concentration is above 0.6%, the additive is excessive, increasing costs. Only when the ADDI concentration is 0.5% is the leveling effect optimal, the marks are completely removed, and the color difference ΔE < 1.5.

[0062] Third water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0063] Grading and texturing: This involves treatment with hydroxides and alcohol solvents; wherein the hydroxide includes sodium hydroxide, and the alcohol solvent includes isopropanol. Specifically, the process temperature is set to 75-80℃, for example, any value between 75℃ and 80℃, such as 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, etc. The washing time is 30-40 seconds, for example, any value between 30s, 31s, 32s, 33s, 34s, 35s, 36s, 37s, 38s, 39s, 40s, or 30-40s, preferably 35s. The initial NaOH concentration is selected as 0.8-1.2%, for example, any value between 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, or 0.8-1.2%, preferably 1.0%. The initial IPA concentration is 2-3%, for example, any value between 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or 2-3%, preferably 2.5%. The initial flocking conditioner concentration is selected as 0.15%, and the self-replenishing NaOH concentration is selected as 0.02-0.06%, for example, any value between 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, or 0.02%-0.06%, preferably 0.04%. The self-replenishing IPA concentration is selected as 0.01-0.04%, for example, any value between 0.01%, 0.02%, 0.03%, 0.04%, or 0.01-0.04%, preferably 0.03%. A continuous circulation, basketless bubbling mode is used. By using gentle texturing to optimize the surface texture of silicon wafers, the problems of whitening and color difference after cleaning are solved. Conventional processes do not have this graded texturing step, and the color difference ΔE of silicon wafers after cleaning is greater than 3.0, resulting in a high defect rate.

[0064] In this disclosure, when the process temperature is below 75℃, the time is below 30s, the NaOH concentration is below 0.8%, and the IPA concentration is below 2%, the texturing effect is insufficient, and color difference cannot be eliminated. When the process temperature is above 80℃, the time is above 40s, the NaOH concentration is above 1.2%, and the IPA concentration is above 3%, the texturing thinning exceeds the standard, with the total silicon wafer thinning exceeding 5μm. Only when the process temperature is 75-80℃, the time is 30-40s, the initial NaOH concentration is 0.8-1.2%, the IPA concentration is 2-3%, and the self-compensating concentration is matched, the texturing effect is optimal, with a color difference ΔE < 1.5, thinning ≤ 1μm, and total thinning ≤ 5μm.

[0065] Fourth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0066] Alkaline washing: Cleaning is performed using hydroxides and oxidants, wherein the hydroxide includes sodium hydroxide and the oxidant includes hydrogen peroxide. Specifically, the cleaning time is 150-200 seconds, the temperature is 60-68°C, and the initial hydroxide concentration is selected as 0.7-2%, for example, any value between 0.7%, 1%, 1.5%, 2%, or 0.7-2%; preferably 1%. The initial hydrogen peroxide concentration is 1.3-2.5%, preferably any value between 1.3%, 1.5%, 1.8%, 2%, 2.5%, or 1.3-2.5%, preferably 1.8%. The self-replenishing hydroxide concentration is selected as 0.015-0.04%, for example, any value between 0.015%, 0.02%, 0.03%, 0.03.5%, 0.04%, or 0.015-0.04%. Preferably 0.025%. The concentration of the self-replenishing hydrogen peroxide is selected from 0.02-0.08%, for example, any value between 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.02-0.08%; preferably 0.05%, using a continuous circulation, basket bubbling mode. Alkaline washing removes residual reaction products and simultaneously cleans organic contaminants from the surface.

[0067] In this disclosure, when the process temperature is below 60℃, the NaOH concentration is below 0.7%, the H2O2 concentration is below 1.3%, the self-replenished NaOH concentration is below 0.015%, and the self-replenished H2O2 concentration is below 0.02%, the alkaline washing effect will decrease, reaction products will remain, and subsequent electrical performance will be abnormal. Conversely, when the process temperature is above 68℃, the NaOH concentration is above 2%, the H2O2 concentration is above 2.5%, the self-replenished NaOH concentration is above 0.04%, and the self-replenished H2O2 concentration is above 0.08%, the hydrogen peroxide will decompose too quickly, leading to excessive alkaline etching and excessive silicon wafer thinning.

[0068] Fifth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0069] Second pickling: This includes cleaning with HF. Specifically, the cleaning time is 150-400 seconds, preferably 300 seconds. The initial HF concentration is 0.8-4%, for example, any value between 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 0.8-4%; preferably 2%. The self-replenishing HF concentration is 0.05-0.3%, for example, any value between 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or 0.05-0.3%, preferably 0.1%. A continuous circulation, basketless bubbling mode is used. HF neutralizes residual alkali and simultaneously removes the surface oxide layer.

[0070] In this disclosure, when the time is less than 150 seconds, the HF concentration is less than 0.8%, and the self-replenishing HF concentration is less than 0.05%, resulting in incomplete neutralization of alkali residue and incomplete removal of the surface oxide layer (poor dehydration). Conversely, when the time is greater than 400 seconds, the HF concentration is greater than 4%, and the self-replenishing HF concentration is less than 0.3%, leading to chaotic operation of the overall robotic arm and chemical waste. Only when the time is between 150 and 400 seconds, the HF concentration is 2%, and the self-replenishing HF concentration is 0.1%, is the oxide layer completely removed, and the dehydration is optimal.

[0071] The sixth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 100-150 seconds and use the overflow mode with a basket.

[0072] Slow lifting: Set the process temperature to 20-30℃, use a robotic arm to lift, and use a straight basket overflow mode.

[0073] It should be noted that all three types of reworked sheets mentioned above are dried after slow lifting. The drying method is conventional drying, for example, drying temperature of 95℃ and drying time of 600s.

[0074] The performance testing methods are as follows: efficiency loss, Uoc(v), Isc(A), Rs(Ω), Rsh(Ω), FF(%) and conversion efficiency are efficiency-related items, and are tested using an IV tester. The testing method is the industry-standard testing method.

[0075] Rework yield, oxidation, dirt and other contamination are yield-related items, which are tested using an EL tester and the testing method is the industry standard test method.

[0076] Color difference and residual marks are appearance-related items, and are tested using front and back AOI tests, which are industry-standard testing methods.

[0077] The total thinning amount is measured using the machine's built-in weighing instrument or an electronic scale.

[0078] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0079] Example 1 This embodiment provides a cleaning method for rework wafers, specifically type A rework wafers, which are rework wafers before boron expansion. Wafers are processed in batches of 500. The following is the cleaning process for one batch: Water washing: Use deionized water to rinse off desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds. Use basket overflow mode.

[0080] Slow lifting: The process temperature is set to 25℃, and a robotic arm is used for lifting. The overflow mode uses a single basket overflow.

[0081] Drying: Set the process temperature to 95℃ and the drying time to 600 seconds, and use conventional drying methods.

[0082] Example 2 This embodiment provides a cleaning method for rework sheets, which are type B rework sheets containing a poly film, a boron layer, and a passivation film. 500 sheets are processed in a batch. The following is the cleaning process for one batch: First water rinse: Use deionized water to rinse off the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0083] First pickling: cleaning time 1800s, initial HF concentration selected as 6%, initial HCl concentration selected as 3%, initial rework additive concentration (purchased from Topband) selected as 3%, self-replenishing HF concentration selected as 0.05%, self-replenishing HCl concentration selected as 0.02%, self-replenishing rework additive concentration selected as 0.03%, using continuous circulation, basketless bubbling mode.

[0084] Second water wash: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0085] Graded flocking: The process temperature is set at 78℃, the washing time is 35s, the initial NaOH concentration is selected as 1.0%, the initial IPA concentration is selected as 2.5%, the initial flocking conditioner (purchased from Hangzhou Xiaochen Technology Co., Ltd.) concentration is selected as 0.15%, the self-replenishing NaOH concentration is selected as 0.04%, and the self-replenishing IPA concentration is selected as 0.03%. The process is carried out in a continuous circulation, basketless bubbling mode.

[0086] Third water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0087] Alkaline washing: washing time 160s, temperature 65℃, initial sodium hydroxide concentration selected as 1%, initial hydrogen peroxide concentration selected as 1.8%, self-replenishing sodium hydroxide concentration selected as 0.025%, self-replenishing hydrogen peroxide concentration selected as 0.05%, using continuous circulation and basket bubbling mode.

[0088] Fourth water wash: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0089] Second pickling: cleaning time 300s, initial HF concentration 2%, self-replenishing HF concentration 0.1%, using continuous circulation, basketless bubbling mode.

[0090] Fifth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0091] Slow lifting: The process temperature is set to 25℃, and a robotic arm is used for lifting. The overflow mode uses a single basket overflow.

[0092] Drying: Set the process temperature to 95℃ and the drying time to 600 seconds, and use conventional drying methods.

[0093] Example 3 This embodiment provides a cleaning method for rework sheets, specifically Class C rework sheets containing laser residue, and specifically Polyfing laser-marked rework sheets. The sheets are arranged in batches of 500. The following describes the cleaning process for one batch: First water rinse: Use deionized water to rinse off the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0094] First pickling: cleaning time 1800s, initial HF concentration selected as 6%, initial HCl concentration selected as 3%, initial rework additive concentration (purchased from Topband) selected as 3%, self-replenishing HF concentration selected as 0.05%, self-replenishing HCl concentration selected as 0.02%, self-replenishing rework additive concentration selected as 0.03%, using continuous circulation, basketless bubbling mode.

[0095] Second water wash: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0096] Alkali polishing: The process temperature is set to 70℃, the time is set to 480s, the initial NaOH concentration is selected as 5%, the initial ADDI concentration is selected as 0.5%, the self-replenishing NaOH concentration is selected as 0.09%, and the self-replenishing ADDI concentration is selected as 0.05%. The process is carried out in a continuous circulation, basketless bubbling mode.

[0097] Third water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0098] Graded flocking: The process temperature is set at 78℃, the washing time is 35s, the initial NaOH concentration is selected as 1.0%, the initial IPA concentration is selected as 2.5%, the initial flocking conditioner concentration is selected as 0.15%, the self-replenishing NaOH concentration is selected as 0.04%, and the self-replenishing IPA concentration is selected as 0.03%. The process is carried out in a continuous circulation, basketless bubbling mode.

[0099] Fourth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0100] Alkaline washing: washing time 160s, temperature 65℃, initial NaOH concentration 1%, initial hydrogen peroxide concentration 1.8%, self-replenishing NaOH concentration 0.025%, self-replenishing hydrogen peroxide concentration 0.05%, using continuous circulation and basket bubbling mode.

[0101] Fifth water rinse: Use deionized water to rinse away the desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds and use the overflow mode with a basket.

[0102] Second pickling: cleaning time 300s, initial HF concentration 2%, self-replenishing HF concentration 0.1%, using continuous circulation, basketless bubbling mode.

[0103] The sixth water rinse: Deionized water is used to rinse off the desorbed impurities and residual chemicals on the silicon wafer surface. The set time is 120 seconds, and the overflow mode uses basket overflow.

[0104] Slow lifting: The process temperature is set to 25℃, and a robotic arm is used for lifting. The overflow mode uses a single basket overflow.

[0105] Drying: Set the process temperature to 95℃ and the drying time to 600 seconds, and use conventional drying methods.

[0106] Examples 4-5 Examples 4-5 provide a cleaning method for reworked wafers. This cleaning method is the same as the cleaning method provided in Example 2, both for cleaning type B reworked wafers. The difference lies in the specific reworked wafers and the different cleaning conditions, as detailed below: Example 4: Type B rework sheets include only Poly film.

[0107] First pickling: cleaning time 1700s, initial HF concentration 4%, initial HCl concentration 2%, initial rework additive (purchased from Topband) concentration 2%, self-replenishing HF concentration 0.04%, self-replenishing HCl concentration 0.01%, and self-replenishing rework additive concentration 0.01%.

[0108] Graded flocking: The process temperature is set at 76℃, the washing time is 30s, the initial NaOH concentration is selected as 1.2%, the initial IPA concentration is selected as 2%, the initial flocking conditioner (purchased from Hangzhou Xiaochen Technology Co., Ltd.) concentration is selected as 0.15%, the self-replenishing NaOH concentration is selected as 0.03%, and the self-replenishing IPA concentration is selected as 0.02%.

[0109] Alkaline washing: washing time 160s, temperature 62℃, initial sodium hydroxide concentration selected as 1.5%, initial hydrogen peroxide concentration selected as 2%, self-replenishing sodium hydroxide concentration selected as 0.03%, and self-replenishing hydrogen peroxide concentration selected as 0.08%.

[0110] All other operations and conditions are the same as in Example 2.

[0111] Example 5: Type B rework sheet includes a poly film and a boron layer.

[0112] First pickling: cleaning time 1800s, initial HF concentration selected as 8%, initial HCl concentration selected as 5%, initial rework additive concentration (purchased from Topband) selected as 5%, self-replenishing HF concentration selected as 0.08%, self-replenishing HCl concentration selected as 0.05%, and self-replenishing rework additive concentration selected as 0.05%.

[0113] Graded flocking: The process temperature is set at 75℃, the washing time is 32s, the initial NaOH concentration is selected as 0.8%, the initial IPA concentration is selected as 3%, the initial flocking conditioner (purchased from Hangzhou Xiaochen Technology Co., Ltd.) concentration is selected as 0.15%, the self-replenishing NaOH concentration is selected as 0.08%, and the self-replenishing IPA concentration is selected as 0.03%.

[0114] Alkaline washing: washing time 160s, temperature 68℃, initial sodium hydroxide concentration selected as 2%, initial hydrogen peroxide concentration selected as 1.3%, self-replenishing sodium hydroxide concentration selected as 0.04%, and self-replenishing hydrogen peroxide concentration selected as 0.03%.

[0115] All other operations and conditions are the same as in Example 2.

[0116] Examples 6-7 Examples 6-7 provide a cleaning method for reworked wafers. This cleaning method is the same as the cleaning method provided in Example 3, both cleaning type C reworked wafers. The difference lies in the specific reworked wafers and the different cleaning conditions, as detailed below: Example 6: Type C rework wafers also include photoresist.

[0117] Before the first water wash, the adhesive is removed. The adhesive removal process includes: a process temperature of 100℃, a washing time of 1800s, an initial H2SO4 concentration of 80%, an initial H2O2 concentration of 20%, a self-replenishing H2SO4 concentration of 0.1%, and a self-replenishing H2O2 concentration of 0.1%, using a continuous circulation and basket bubbling mode. All other operations are the same as in Example 3.

[0118] Example 7: Type C rework piece is a BC laser isolation groove marked rework piece.

[0119] Alkali polishing: The process temperature was set to 72℃, the time to 600s, the initial NaOH concentration was 6%, the initial ADDI concentration was 0.45%, the self-replenishing NaOH concentration was 0.1%, and the self-replenishing ADDI concentration was 0.045%. A continuous circulation, basketless bubbling mode was used. All other operations were the same as in Example 3.

[0120] Comparative Example 1 This comparative example provides a method for cleaning rework sheets. The rework sheets cleaned by this method are 500 pieces of type B rework sheets from Example 2. The flowchart of the cleaning method is shown below. Figure 2 The process is as follows: pickling → water washing → alkali washing → water washing → post-pickling → water washing → slow lifting → drying. The specific process is as follows: Pickling: Cleaning time 3600s, initial HF concentration 7%, initial additive concentration 3%, self-replenishing HF concentration 0.3%, self-replenishing additive concentration 0.15%, using continuous circulation, basketless bubbling mode.

[0121] Water washing: Use deionized water to rinse off desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds. Use basket overflow mode.

[0122] Alkali washing: cleaning time 160s, temperature 62℃, initial alkali concentration selected as 0.8%, initial hydrogen peroxide concentration selected as 1.2%, self-replenishing alkali concentration selected as 0.015%, self-replenishing hydrogen peroxide concentration selected as 0.03%, using continuous circulation and basket bubbling mode.

[0123] Water washing: Use deionized water to rinse off desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds. Use basket overflow mode.

[0124] Pickling: Cleaning time 300s, initial HF concentration 3%, initial HCl concentration 1.5%, self-replenishing HF concentration 0.25%, self-replenishing HCl concentration 0.15%, using continuous circulation, basketless bubbling mode.

[0125] Water washing: Use deionized water to rinse off desorbed impurities and residual chemicals on the silicon wafer surface. Set the time to 120 seconds. Use basket overflow mode.

[0126] Slow lifting: The process temperature is set to 25℃, and a robotic arm is used for lifting. The overflow mode uses a single basket overflow.

[0127] Drying: Set the process temperature to 95℃ and the drying time to 600 seconds, and use conventional drying methods.

[0128] Comparative Example 2 This comparative example provides a method for cleaning rework sheets. The rework sheets cleaned by this method are the Class C rework sheets (500 sheets per batch) of Example 3. The cleaning method of this comparative example is the same as the cleaning method provided in Comparative Example 1.

[0129] Performance tests were conducted on the reworked wafers after cleaning in Examples 1-3, 6-7 and Comparative Examples 1-2. The test results are shown in Tables 1-3 below.

[0130] See the image of the reworked piece after cleaning in Example 3. Figure 3 For comparison example 1, see the image of the reworked piece after cleaning. Figure 4 For comparison example 2, see the images of the reworked pieces before and after cleaning. Figure 5 and Figure 6 .

[0131] Table 1 Test Results 1

[0132] Table 2 Test Results 2

[0133] Table 3 Test Results 3

[0134] In summary, the conventional process used in the comparative example suffers from excessive thinning, significant efficiency loss, and noticeable color difference. It fails to effectively remove laser markings from Class C rework sheets, resulting in a low overall yield and high EL defects. In contrast, the three embodiments disclosed in this paper employ a tiered process for different types of rework sheets, strictly controlling the thinning amount within the standard range. This results in an efficiency loss ≤0.2%, a color difference ΔE <1.5, a rework yield ≥97%, and EL defects reduced to below 0.2%, with a conversion efficiency improvement of 0.14-0.15% compared to the comparative example.

[0135] This disclosure utilizes a graded cleaning process to match specific processes to different types of rework sheets, and integrates graded texturing to solve appearance problems. It addresses the pain points of poor adaptability, poor appearance, low efficiency, and low yield of conventional processes, achieving full coverage of single-machine rework sheets for all categories, significantly reducing production costs, increasing the reuse value of rework sheets, and fully adapting to mass production needs.

[0136] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A cleaning method compatible with reworked cells of multiple battery types, characterized in that, include: The rework pieces are classified according to their degree of contamination, and then different cleaning treatments are performed based on the classification. The classification and cleaning treatments are as follows: (1) Class A reworked sheets: The surface is only contaminated, without Poly film, boron layer and passivation film; The cleaning process for the Class A rework pieces includes: water washing and slow lifting; (2) Class B rework sheets: containing at least one of Poly film, boron layer and passivation film; The cleaning process for the Class B rework pieces includes: first water wash, first acid wash, second water wash, graded flocking, third water wash, alkaline wash, fourth water wash, second acid wash, fifth water wash, and slow lifting; (3) Category C rework pieces: containing laser residue; The cleaning process for the Class C rework pieces includes: first water wash, first acid wash, second water wash, alkaline polishing, third water wash, graded flocking, fourth water wash, alkaline wash, fifth water wash, second acid wash, sixth water wash, and slow lifting.

2. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The first acid pickling process in the cleaning process of the B-type rework pieces includes cleaning with HF and HCl; Preferably, the conditions for the first pickling during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of HF is 3-8%; the initial concentration of HCl is 1-5%; the initial concentration of rework additive is 1-5%; (2) the self-replenishing concentration of HF is 0.03-0.08%; the self-replenishing concentration of HCl is 0.01-0.05%; the self-replenishing concentration of rework additive is 0.01-0.05%.

3. The cleaning method for compatible reworked cells of multiple battery types according to claim 1, characterized in that, The grading and texturing process during the cleaning of the Class B rework sheets includes treatment with hydroxides and alcohol solvents; preferably, the hydroxides include sodium hydroxide and the alcohol solvents include isopropanol. Preferably, the grading and texturing conditions during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.8-1.2%, and the initial concentration of the alcohol solvent is 2-3%; (2) the self-replenished concentration of the hydroxide is 0.02-0.06%, and the self-replenished concentration of the alcohol solvent is 0.01-0.04%; (3) the temperature is 75-80℃, and the time is 30-40s.

4. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The alkaline washing process in the cleaning process of the B-type rework sheets includes: cleaning with hydroxide and oxidant, preferably, the hydroxide includes sodium hydroxide and the oxidant includes hydrogen peroxide; Preferably, the alkaline washing conditions during the cleaning process of the B-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.7-2% and the initial concentration of the oxidant is 1.3-2.5%; (2) the self-replenished concentration of the hydroxide is 0.015-0.04% and the self-replenished concentration of the oxidant is 0.02-0.08%.

5. The cleaning method for compatible reworked cells of multiple battery types according to claim 1, characterized in that, The second pickling process in the cleaning process of the Class B rework pieces includes cleaning with HF. Preferably, the conditions for the second acid washing during the cleaning process of the B-type rework piece meet at least one of the following requirements: (1) the initial concentration of the HF is 0.8-4%; (2) the self-replenishing concentration of the HF is 0.05-0.3%; and (3) the cleaning time is 150-400s.

6. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, If the C-type rework sheet contains photoresist, the cleaning process of the C-type rework sheet further includes: removing the photoresist before the first water wash; Preferably, the degumming process includes: using an oxidizing agent and a strong acid for degumming; Preferably, the oxidant includes hydrogen peroxide, and the strong acid includes sulfuric acid; Preferably, the conditions for degumming meet at least one of the following requirements: (1) the initial concentration of the strong acid is 65-85% and the initial concentration of the oxidant is 15-25%; (2) the concentration of the self-replenishing strong acid is 0.05-0.15% and the concentration of the self-replenishing oxidant is 0.05-0.15%; (3) the temperature is 90-120℃ and the time is 1800-2000s.

7. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The first acid pickling process in the cleaning process of the C-type rework pieces includes cleaning with HF and HCl; Preferably, the conditions for the first pickling during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of HF is 3-8%; the initial concentration of HCl is 1-5%; the initial concentration of rework additive is 1-5%; (2) the self-replenishing concentration of HF is 0.03-0.08%; the self-replenishing concentration of HCl is 0.01-0.05%; the self-replenishing concentration of rework additive is 0.01-0.05%.

8. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The alkaline polishing process during the cleaning of the C-type rework sheets includes: alkaline polishing using hydroxides and ADDI; Preferably, the hydroxide comprises sodium hydroxide; The alkaline polishing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 5-7%; the initial concentration of the ADDI is 0.4-0.5%; (2) the self-replenished concentration of the hydroxide is 0.08-0.1% and the self-replenished concentration of the ADDI is 0.04-0.05%; (3) the temperature is 70-75℃ and the time is 450-600s.

9. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The graded texturing of the C-type rework sheets includes treatment with hydroxides and alcohol solvents; preferably, the hydroxides include sodium hydroxide and the alcohol solvents include isopropanol. Preferably, the grading and texturing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.8-1.2%, and the initial concentration of the alcohol solvent is 2-3%; (2) the self-replenished concentration of the hydroxide is 0.02-0.06%, and the self-replenished concentration of the alcohol solvent is 0.01-0.04%; (3) the temperature is 75-80℃, and the time is 30-40s.

10. The cleaning method for compatible rework cells of multiple battery types according to claim 1, characterized in that, The alkaline washing of the C-type rework sheets is carried out using hydroxides and oxidants. Preferably, the hydroxides include sodium hydroxide and the oxidants include hydrogen peroxide. Preferably, the alkaline washing conditions during the cleaning process of the C-type rework sheet meet at least one of the following requirements: (1) the initial concentration of the hydroxide is 0.7-2%, and the initial concentration of the oxidant is 1.3-2.5%; (2) the self-replenished concentration of the hydroxide is 0.015-0.04%, and the self-replenished concentration of the oxidant is 0.02-0.08%; (3) the temperature is 60-68℃; Preferably, the second pickling process in the cleaning process of the C-type rework piece includes cleaning with HF; Preferably, the conditions for the second acid washing during the cleaning process of the C-type rework piece meet at least one of the following requirements: (1) the initial concentration of the HF is 0.8-4%; (2) the self-replenishing concentration of the HF is 0.05-0.3%; and (3) the cleaning time is 150-400s.

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